Automobile manufacturers face increasing final assembly complexity due to expanding model portfolios, customized configurations, and emerging powertrain technologies. Conventional assembly lines struggle to absorb process variability efficiently. In response, this study introduces a hybrid assembly concept that integrates cycle-based line segments with flexible matrix segments to combine efficiency with adaptability. A structured scoring-based decision methodology is developed to allocate process modules based on criteria such as process time variance, variant diversity, labor requirements, and precedence constraints. The approach is validated through a case study at a German automotive OEM. Results show that 11 out of 17 assembly clusters benefit from matrix integration, with reduced cycle time losses and improved flexibility. The findings demonstrate the practical applicability of the methodology and its potential to support the transition toward future-oriented, modular assembly systems.